Biological Attacks on Underground Hydroelectric Pump Storage Power Stations

Studies have shown the unconditional danger of biological attacks on underground hydroelectric pumped-storage power stations. A hypothetical list of biological damage to water conduits and dams is determined. Relevant predictions are given, as well as accident events of hydraulic structures are described. A universal scheme for the application of hazard protection measures, which can be comprehensive, has been developed. Praemonitus praemunitus – precautions should be taken.


Introduction
The attractiveness of using abandoned mines in the construction of underground hydroelectric pumped-storage power stations (UHPSPS) consists in reduction or exception of reservoir preparation works. However, there are doubts about the safety of this innovative technology.
Firstly, the water pumped to the upper reservoir is aerated, and its initial chemical composition evolves to be in equilibrium with the atmosphere leading to an increase of pO2 (power of hydrogen) and associated chemical reactions. In addition, this water is released into the underground reservoir and may react with the surrounding fractured medium and with the water occupying the reservoir. This may induce the deposition or dissolution of minerals and the associated impacts, e.g., reduction or increase in pH. In the specific case of abandoned coal mines, where sulfides are common, an increase of pO2 in the upper reservoir may induce sulfide oxidation when the water is released in the underground reservoir. This fact would lead to very low pH values (i.e., acidification) and then affect the surrounding groundwater quality through the infiltration exchange fluxes between the underground reservoir and the surrounding geological layers [1,2].
Secondly, the construction of UHPSPS requires the use of a lower underground reservoir in the form of drifts (horizontal underground mine). This could lead to problems in the discharge of water from the turbine due to the resistance implied by the lower reservoir, since it is not at atmospheric pressure. This resistance, in case of being high, could require a higher pressure for the turbine to complete the filling of the tunnel network [3].
Thirdly, at the end of the drift, the total reflection of the falling wave occurs. In theory, the waves double at those positions [4]. Consider that in the wet liquidation of mines, in which the volume produced is filled with water, a fractured-reservoir array is formed; it acts as a single fractured zone. Normal fluctuations of the water masses can contribute to increasing the seismicity of the created depression zone [5].
Current global warming is one of the factors that accelerates the invasive process. There is information on the "aggression" of invasive species in relation to local flora and fauna. The danger catalyst can be the anthropogenic impact, characterized by the promotion of climate change, artificial modification of the environment. There is evidence of attacks on communication cables, radioelectronic and electronic computing means that can cause invasive and indigenous populations of organisms or their communities, plants under global warming [6].
The aim of the paper is to study biological threats to underground hydroelectric pumped-storage power stations and possible bioaggression protection measures.
To achieve the aim, the following objectives must be accomplished: To determine a list of threats; 2. To analyze their destructive effect; 3. To consider countermeasures.

Method
Fig . 1 shows the classification of biological damage to radioelectronic and electronic devices, Table 1 provides the explanation.  associated with preliminary chemical destruction of the starting material of sometimes only one component (usually a low molecular weight compound, for example a plasticizer, stabilizer) by enzymes. Such destruction opens the way for physicochemical corrosion, leads to a deterioration in the thermodynamic properties of the material and its mechanical destruction under the action of operational loads 3.2. Chemical effects of released substances chemical effect of metabolic products of microorganisms, which increases the aggressiveness of the environment, stimulates corrosion processes 4. Biocorrosion biocorrosion at the material-organism interface due to the action of amino and organic acids, as well as hydrolysis products; it is based on electrochemical processes of metal corrosion under the action of microorganisms The presence of radioelectronic and electronic means in the HPSPS is the basis for using the classification of their biological damage in the analysis of damage to the pumped-storage station.

Biodamage to hydropower stations
Assume the default unconditional biological vulnerability of radioelectronic and computing electronic means of hydropower stations and pay attention to biological damage to water conduits and dams. Some dam failures related to animal and plant activities are shown in Table 2. Uncontrolled infiltration through animal burrows on the downstream face, resulting in erosion Eleva Roller Mill, Wisconsin, USA, 03/1994 [9] Piping; biological attack (i.e., bush, tree growth) Lake Montonia Dam, North Carolina, USA, 02/1995 [9] Infiltration was noted in three locations, in particular at the blown over tree under the root ball downstream of the drain pipe near the emergency spillway channel Oaklawn Pond Dam, Texas, USA, 11/1996 [9] The dam was severely damaged when strong winds uprooted several trees on the embankment. An inspection revealed that the upheaving of the root mass, aggravated by beavers damage, had left gaps in the crest and on the slopes of the dam Pischieri Pond Dam, Cleveland, Ohio, USA, 1999 Muskrat burrows Table 3 shows the description of biological damage to hydropower stations in the proposed form of Table 1. accumulated in the catchment area [11].
The dimensions comparable to the dimensions of gates and water conduits determine the danger of their destruction by a ram. 1.2. "Gnawing" and infiltration Some dam failures caused by digging holes and seeping through tree roots, associated with animal and plant activities, are shown in Table   2.
Examples of typical damage to earth dams by rodents are systematized and presented in the paper [8].
In the early 2000s, the United States conducted a survey of experts on the danger that vegetation poses to dams. The analysis of accidents revealed their causes [12]:  uprooted trees that produce large voids and reduced freeboard; and/or reduced x-section for maintaining stability;  decaying roots that create infiltration paths and internal erosion problems;  obstructing emergency spillway capacity;  [13].
No damage to hydropower stations due to biopollution was detected. Microorganisms stimulate the corrosion process using environmental components or corrosion products during their metabolism. Examples include the ability of sulfate-reducing bacteria to exploit hydrogen and the ability of iron bacteria to oxidize Fe 2+ to Fe 3+ , and thereby permanently support the corrosion process. Microorganisms can also evolve aggressive substances for metals (evolution of hydrogen sulfide by sulfate-reducing bacteria, production of sulfuric acid by sulfate-oxidizing bacteria, etc.). Only biofilm formation, enabling the formation of concentration corrosion cells, shall be considered as a physical change at the metal-environment interface [21].

Protection of hydroelectric power plants against biodamage
It must be admitted that natural disasters are often inevitable. So, optimization of their negative consequences becomes a practical task. Hazard reduction (protective measures) may include short-term hazard forecasting and warning; long-term forecasting and establishment of strict building codes in high-risk areas. The scheme of application of protection measures for radioelectronic and computing electronic means as a part of hydropower stations is the reason for using it in UHPSPS protection (Fig. 2). The proposed scheme is designed for developing an action plan to prevent hazards of interferences, or at least reduce their negative consequences. Short-term hazard forecasting is performed to alert the public and collect data. The data are used in long-term forecasting. It is used in assessing risks and their acceptable levels to declare the safety of facilities, make decisions on their location and operation, develop prevention measures against accidents and prepare to respond to them. The list of protection measures includes:  application of hazard-resistant materials and structures;  hazard interception, which involves shielding the object or its most vulnerable and critical elements from danger, or shielding danger from the object, as well as counteracting the danger;  maintenance systems reconfiguration (power supply, ventilation and air conditioning, fire alarm, fire extinguishing, warning, etc.).
The concept of reasonable sufficiency should be used as a basic criterion when developing a protection project. Its purpose is to ensure that the biological safety requirements for underground pumped-storage power stations are met with a minimum of funds and protection measures in the face of expected impact.
The development of protection measures against the effects of damaging factors depends on:  the intensity of biological attacks in the appropriate area (zoning planning);  estimation of objects vulnerability;  the cost of object protection equipment, as this can be an important criterion for complicating the protection scheme.

Discussion
The result of infiltration along the trees and shrubs roots is similar to the result of digging holes (gnawing). Examples show that biodamage is divided according to the origin -animal-related and plant-related.
No cases of destruction and contamination of water conduits and dams have been found, but this probability should not be ruled out. There are events in life that are hard to imagine. In Australia, for example, a transport drone delivering small goods was attacked by a crow.
The scheme of application of protection measures against biological hazards, which can be comprehensive, is developed. Hazards can be eliminated or reduced by several protection methods. Conversely, the same measures can be used to eliminate different hazards of both natural and anthropogenic origin.
The fundamental principle of bioethics "First, do no harm (Primum non nocere)" warns against ill-considered actions. Theoretical calculations on biological damage to underground pumped-storage power stations are one of the aspects of the comprehensive impact of innovative energy conservation technology on the environment. The proposed paper raises an issue that requires more detailed and inquisitive research.